"Flight software is a kind of embedded real-time software, a field that has seen exponential growth since its inception. In some areas of NASA, flight software is growing by a factor of ten every ten years. Estimates for Orion’s primary flight software exceed one million lines of code."

...

"The newest fighter still under development, the F-35 Joint Strike Fighter, will, according to one source, have 5.7 M lines of code."

“While technology can change quickly, getting your people to change takes a great deal longer. That is why the people-intensive job of developing software has had essentially the same problems for over 40 years. It is also why, unless you do something, the situation won’t improve by itself. In fact, current trends suggest that your future products will use more software and be more complex than those of today. This means that more of your people will work on software and that their work will be harder to track and more difficult to manage. Unless you make some changes in the way your software work is done, your current problems will likely get much worse.”

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flight software is growing by a factor of ten every ten years. Estimates for Orion’s primary flight software exceed one million lines of code."

"The newest fighter still under development, the F-35 Joint Strike Fighter, will, according to one source, have 5.7 M lines of code."

Complexity isn't defined by the quantity of lines of code, but by how difficult it is for an engineer to understand it. I can obfuscate a single line of code and completely lose anyone